A biological product, as the term is used herein, is a product that may be prepared using living organisms. For example, virus or bacteria may be produced for use in vaccines by using live tissue cells as a substrate. Humulin is another biological product; it is synthesized in a non-disease-producing strain of Escherichia coli bacteria that has been genetically altered to produce human insulin.
Most biological products are prone to degradation such as thermal, photochemical, or oxidative degradation. Because biological products such as vaccines and insulin need to be distributed worldwide, and because ambient temperatures in different regions vary greatly, there exists a need to stabilize vaccine and other biological preparations for transportation and use. Several stabilization methods for vaccines have been used in the past.
One strategy has been the use of very low temperatures, for example, −10 degrees Celsius (−10° C.) to −70 degrees Celsius (−70° C.). However, lack of availability of facilities for such low temperature storage limits the practicality of this approach.
Another method is lyophilization, an expensive procedure. Lyophilized vaccines are reasonably stable and can be stored at about 4° to 8° C. However, because the lyophilized vaccine must be reconstituted prior to use, the liquid, reconstituted preparation loses potency while standing at room temperature. This can result in insufficient titer to confer immunity and may therefore result in the failure of an immunization program.
The use of chemical stabilizers added to the vaccine has been yet another approach. The stabilizers are used in conjunction with either lower temperature storage or lyophilization methods. However, none of the available stabilizers imparts the desired enhanced sustained level of stability. Further, many of these chemical stabilizers, such as albumin, and gelatin, are of animal origin, and carry a risk that vaccines in which these stabilizers are incorporated may be contaminated with various agents of animal origin. Such contaminants may carry a risk of an allergic reaction in the patient receiving the vaccine, and may also cause batch to batch variability in the vaccines stabilized with animal origin chemicals.
Thus, there is an on-going need for an improved chemical stabilizer for liquid and lyophilized viral vaccines and other biological products. There is also a need for improved lyophilized or liquid viral vaccines having prolonged storage stability over a range of temperatures, and having diminished reduction in titer. There is a further need to enhance the immunological activity of vaccine preparations.